Ferromagnetic material



July 26, 1960 Filed Aug. 9, 1956 G. H. JONKER EI'AL 2,946,753

FERROMAGNETIC MATERIAL 5 Sheets-Sheet 1 gzo oo T 50 I00 SOO IOOO Frcg.(Mc/$eO) FIGI INVENTORS GERARD I'EINRICH JWKER HENRICUS PETRUS JOHANNES WhN POUL BERNARD BRAUN AGENT y 1960 G. H. JONKER ETALY 2,946,753

FERROMAGNETIC MATERIAL 7 Filed Aug. 9, 1956 5 Sheets-Sheet 2 IOOT IO 50 I00 500 I000 Fr cg. (Me/sec) FIG. 2

INVENTORS GERARD nsmmcu JONKER nsumcus PETRUS JOHANNES vlun POUL mm BRAUN AGENT y 1960 e. H. JONKER ET AL 2,946,753

FERROMAGNETIC MATERIAL Filed Aug. 9, 1956 5 Sheets-Sheet 5 ago IO 50 I00 5 Frcq (Me/sec) G RARD HE R E JOHANIEWIJN HENRICUS PET POUL BERN D BRAUN L ah. ug L.

' -Oxidic ferromagnetic materials- These and other objects$of--our invention "parent as the specification progresses.

United States Patent FERROMAGNETIC MATERIAL;

Filed Aug. 9, 1956, Ser. No. 603,136

Claims I priority, application Netherlands Aug. 10,1955

8 Claims. (c1. 2 52--62.5

Our invention relates to oxidic ferromar gireticv mate! rials, to methods of preparing-these materials and to bodies made from these materials. i,

which exhibit high values of initial permeability are known in the art. All

theseniaterials show a-decrease of the initial, permeability in a certain frequency range the position of which in the frequency scaleis related to the low-frequency value of the initial permeability. 'The initial permeability decreases ina frequencyrange the position of which in the frequency scale is higher in proportion as .the value of the initial permeability. at low-frequency is lower. Thus the cores :formed from these materials are not too satisfactory for use at high frequencies.

'. The principal object of our inventiom therefore, is to provide a new and novel class of oxidic, ferromagnetic materials theinitial permeability of which decreases in a much higher positioned frequency range than in the known materials-with an equal low frequency value of the initial permeability.

Another object of our invention is to provide oxidic quencies and which exhibit low losses. 1'

Still anotheriobject of our mvention'is to-ipr'ovide oxidic ferromagnetic materials which may serveas mate ferromagnetic materials which have initial permeabilities Qof more and often materially more than 2 at frequencies rials for magnetic bodies e.g. cores at frequencies of -about.50'mc./ s and often considerably higher frequencies. e w

According to .our invention we have foundjnew and may be replaced for at most one tenth by- Cr and/or Al-ions. Thus, the formula for these materials may be restated as follows:

In the formula M represents one of the aforesaid divalent metals and the subscripts have the following value a less than 0.5 b less than 0.25 a less than 0.25

- f less than 0.6

(e+f) less than 0.6

7 --All these materials have -initial' jpermeabilitiesl which They have initial permeabilities of more and often mate: rially more than 2 at frequencies of about 50 mc./s. and often-considerably higher frequencies. Since they are basically oxidic in nature they are characterized'by high ohmic resistances so that eddy current losses are negligibly small. In addition. to having greatly improved initial permeabilities at high frequencies, particularly above 50 mc./s., the materials of our invention exhibit relatively low residual loss factors (tanfi) at-frequencies above 50 mc./s.

The novel materials of our invention have a rhombqhedric crystal structure of which theunit cell in the hexagonal crystal system has a coaxis of about 43.5 A; and an axis of about 5.9 A. i

While the entire class of our novel materials have improved magnetic properties, particularly in regard to their initial permeabilities, wehave found that materials having a composition BaZn Mg Me Fe mO wherein Oit l, Oyl and 0 (x+y)l and wherein Me is at least-one divalent metal selected from the group consisting of Mn, Fe, Co, Ni and Cu, in which formula the Ba'may be replaced in the aforesaid manner, have even further improved initial permeabilities. I

Weprepare the. novel materials of our invention by heating at a temperature of more. than 1000 C. a finely divided mixture of metallic. oxides in a ratio approximately corresponding to that of the metals in the materials of our invention. Alternatively instead of a metallic oxide we may. use amaterial whichforms an oxidewhen heated. As these oxide-forming materialswe 'may'use carbonates, oxalates and acetates of the metals. More'- "metallic oxides.

Preferably we prepare the novel materials of ourinvention by heating at a temperature of between 1150 .C.

and 1300" C. a finely dividedm-ixture of metallic oxides "and/or oxide-forming materials and/or reaction .pr'od nets of metallic oxides, in a ratio approximately corre- V .'sponding to that of the metalsin the materials of our, invention, 1

As .-,a preformed reaction product of at least two of the {metallic oxides we. preferably use an iron-conta'ming novelmaterials having a -coniposition BaM FeJ O "wherein M is at least one divalent metal selected from 'the group consisting of Mn, Fe, Co, Ni, Cu,' Zn and-Mg. In' the aforesaid formula'Ba may-be replaced-partly by "similar ions, for example Sr, .Ca and Pb, since-the- Ba may be'replaced at amaximum forhalf by Sr or atf-a ."temperature of about 900 C. to 1200 C., the presinteijed .material,heing regroundand resintered several more if desired'before being-subjected to the higher tempera- :process we may. include, various flux agents, for example .silicates.such as pentonite or fluorides such as'calciurnmixtures.

reaction product, which has been produced at lo'w tern- Jperaturo, preferably belovv '1l00 C., and which has a fcrystal structure corresponding with thatzof the mineral. m agnet oplumbite, for example Ba Sr Fe O where- .in Oxl- Q '5 If necessary the mixture of oxides and/or equivalent materials may be presintered, usually at a relatively low tures of the process.

IIlL'OldCF- to facilitate-the sintering operationof-cur fluoride in an amount of from 0.25 to 5 in the starting .Bodies of desired "grinding the sintered material of our invention or the -presinte'fedmaterial, molding the resultant powder .into

the desired shape and sintering the molded .p'rodu'c'twif necessary. A binder such as water, a solution of nitrodo not decrease substantially up to very high frequencies;

1.1 a r divided te slp c invsmisn'is stat s "9 ism-i a cellulose or a solution of carboxymethylcellulose may be further embodiment of the invention the finely -sha pe may be' formed by sintering 'the starting mixtures directly in thedesired shape. Alternatively bodies ofdesired shape may be formed by rebody ofthe desired shape by pressing the relative material together with a binding agent which is capable of being hardened (for example a polyester resin) or an ethoxylin resin followed by hardening the molded body;

Our invention will now be described in greater detail with reference to the following examples and drawing.

,In the drawing, Figs. 1 to are graphs showing the relationship between the values of. the .real portion of initial permeability, 1., and the values of the loss factor, tan 6, to frequency for various embodiments of our invention.

The relationship between the loss factor tan 6 and the real portion of initial permeability, u, will be apparent from the following explanation which forms no part of our invention and which is not to be used in any way to limit the scope of our invention:

The term u" as used herein may .beexplained as 'follows: A sinusoidally alternating magnetic .field with small amplitude will produce a similarly varying inductance in a ferromagnetic body but due to ferromagnetic losses there will be a phase diflerence between the magnetic held and the inductance. Thus the permeability of the ferromagnetic body, ,u, may be represented by a com lex magnitude ,u=p.' The real portion of permeability, ,u, is in phase with the field-applied while the other lags in phase by 90 with respect to the applied field. The loss factor tan 6 can then be defined as IT tan a 7 Example I V Mixtures having the following compositions were pro duced:

(.1) 98.7 gs. of BaCO 245.0 .gs. "of R203, and 46.3 gs.

of. MgCO 2 98.7 gs. of BaCO 245.0 gs. of F6303, and 64.9 gs.

0f v .(3) 98.7 gs. of BaCO 245.0 gs. of Fe O and 63.7 gs.

of NiCO I r (4) 98.7 gs. of BaCO 245.0 gs. of R 0 and 40.8 gs.

of ZnO. a

Of the raw materials the BaCO was substantially pure, the Fe O contained 68.4% by weight of iron, the MgCO 26.2% by weight of magnesium, the C000 45.3% by Weight of cob-alt, the NiCO 46.1% by weight of nickel andthe ZnO 78.4% by weight of zinc.

These mixtures were ground for 16 hours with ethyl alcohol in a chromium-plated iron ball mill. The dried powders were then presintered for two hours at 1050. in oxygen. The reaction products were ground for .16 hours. To these dried powders, a small amount of water 'was then added and rings having an outer diameter of about 35 mms., an inner diameter of about 25 turns. and a height of about 4 mms. were moulded at a'pressure of '1000 kgs./cm. These rings were .sinteredfor two hours in oxygen and then cooled to room temperature within about 4 hours. For the magnesium-, cobaltand nickeleontaining compounds the sintering temperature was 1260" C., and for the zinc-containing compound the sintering temperature was 1240 C. X-ray examination showed that in this manner comparatively pure corn.-

zpeunds having desired structure were obtained. Also small quantities of compoundshaving a spinel crystal structure (probably MgFe O Col-e 0 NiFe O ZnFe O "and also a small quantity of BaFe O were formed. The properties of this series'of compounds are 'indicatedin the table under Nos. 1 to 4. U I Example II V n A n umber of rings of t'hezinc-containing material, described in Example 'I, were sintered for only half an 4 Example III A mixture of 26.0 gs. of BaCO 60.0 gs. of'Fe 0 and 9.5 gs. of NiO was ground with ethyl alcohol in a porcelain ball mill. The dried mixture was pres'intered for 15 hours at 1100 C. in air. This reaction product was then ground again .for half an hour; From this material rings were molded at a pressure of. 1000 kgs./cm. having an outer diameter of about 35 mms., an inner diameter of 25 mms. and a height of about 4 mms., after the addition of a small quantity Ofa solution of nitrocellulose as an organic binder. These rings were s'intered in oxygen at a temperature of 1290 C. and then cooled to room temperature within about 5 hours. An X-ray examination proved thatthe material thus obtained consisted almost entirely of the desired compound BaNi FCG IIa Whilst a small quantity of BaFe O was formed as a second phase. The properties of the rings are indicated in the table under N0. 6.

Example IV Mixtures having the following compositions were produced:

(7) 98.7 gs. of BaCO 245.0 gs. of Fe,o,, 9.2 gs. of

MgCO and 32.6 gs. of .ZnO,

(8) 98.7 gs. of BaCO 245.0 gs. of 1e 0,, 13.0 gs. of

'CocO -and 32.6 gs. of ZnO,

(9) 98.7 gs. of BaCO 245.0 gs. of F6 0 38.2 gs. of

NiCo and 16.3 gs. of ZnO.

. os oe' s n o.sCo.aE eQi1s. 3 as oA s 11 respectively- Also small quantities oftoinpounds having a spinel crystal structure (probably MgFe O CoFe O 'NiFe Og, ZnFe Q were formed. The properties of these compounds are indicatedin the tablennderiNos. 7, 8 and 9.

Example V v y .A mixtureof barium carbonate, strontium carbonate, zinc oxide and ferric oxide in .a .ratioin .aecordancewith the .formula Ba Sr ZnI-Te O was ground -withethyl alcohol in a porcelain ball mill. The dried mixture was presinteredfor 15 hours at 1100" 'C. in air, This reaction product was then ground again for half an hour. .After the addition of a small quantity or a solution of carboxyrnethylcellulose as an organic binder, rings were molded from this material at a pressure of '1000 kgs/cmfl, the rings having an outer diameter of about 35 mms., an inner diameter of about 25 name. and a height of about 4 mms. These rings were sintered in oxygen at a temperature of 1230" C. and then cooled to room. tempera ture within about 4 hours. .By X-ray examination is was found that in this manner a comparatively pure com pound of the desired structure was obtained. The properties of the rings are indicated in thetable under No. 10.

Example'VI In the manner described in Example V, starting from a mixture of barium carbonate, calcium carbonate, zinc oxide and ferric oxide in a ratio in accordance with the formula Ba Ca Znles0 1, a material was produced tity of crystals with spinel crystal structure (probably hour at 1200 C. in oxygen and then cooled to room tem- 1 :iperature within about one hour. The properties of these rings are indicated in the table under N0. '5.

Zn Fe O was obtained as a second phase. The properties of this compound are indicated :inthe table under a ratio in accordance with theitformula A rings are indicated 1 mi M .1

c po w i st asma qu m yotc yst w sp nq crystal structure-(probablyfZnFe 9-1was-obtained as a second phase. The properties of thisfcompo'undare indi cated in the table under-No.42. 1 r

Example VIII" v nrbmnaco, and re p, .in themole'cularratioof 5.6 by heating the mixture' for 15 hours at 900 0. a material was produced which consisted primarilyof the'compound' 7 BaFe O 33 gs. o'fthis materialwas, mixed with 5.'2

which corresponds tothe desiredjcompound' 1 e the product was shaped in the form of ringsat apressure of 1000 kgsjcmfi, which were'firedat'1240" C. in oxygen. By X ray examinationit was found that indeed the desired compound was obtained. The propertiesof the in the table under N0. 13.

Example IX 1 i The compounds am o BaFe Oi 32141.- of the material was mixed with: 6.05 gs. of

BaCO 4.9 gs. of ZnO and 2.33 gs. of C139 which. I corresponds to.'the desired compound BaZnFe Cr O 1 Q (.16) The mixtures were ground for one hour with ethyl carbonate;leadearbonatc ind-'oxide afid ferric oxide 3 alcohol i a Porcelain ball mill and after dryingthey were. presintered for; two hours at 1000? C. in oxygen.

fornfringsv at afpressure of1000 kgs./cm'. which were a a a; w h e g ga moved fired at 1250 C. in oxygen. 'X-raycxamination proved ..b X examination. I entirely of th .ld' sird .10 that, indeed, the desired compounds'we're formed; 1 The propertiesof the rings are indicated in the table under Nca n lfia Many other similar compoundsmay be'produced in an a a O 0 it 9 In the following table, in column 2, under the heading roffMain, Constituent, chemical formulae are indicated, whichwere derived fromthe compositions of ,thejstarting mixtures and from the X-ray examinations. All'rneasuring results were obtained'by carrying out measurements on rings in a demagnetized state at ,room temperatu're'by The graphs of Figs. 1 to 5show the relationship between the real portion of the initialpermeability, ,o', and

and ZnFeQO; were 1.35

tan 6 to frequency for theproducts designated in the table r 7 Y I 1 VI No. Main Constituent d, p, Low 500 Figure e g./em.' 9 cm fre- Mc./s. Mc./s

quency 3. 3 10 ll 10 10 5. 0 10 4 V 4 3. 5 4.0 10 5 5 5 4. 6 I 10 32 21 12' 3. 4 10 12 8. 2 6 4. 2 10 6 5 4 4.7 10f 25- "19 11 '1 .4.8 16 15 13 10 BaZllu.gNlu.4Fs0l1- 4. 6 10 20 19 12 Ba SX'MZnFBsOv 15. 4 14. 7 5.3 Baeu auJaZnFea 12. 3 9. 2 5, 7 BanJsP Ma BaOu 32.6 25.1 10.1 BaCOMZHMFQQOu 7. 9 '7. 2 7. 0 BaZIJFGsOi' 1 14. 2 9.3 7. 2 BaZnFe$.aAlo. O" 13. 8 12. 1 I

BaZnI 05.5(31'0J011 5. 4 4. 2

previously produced by presintering mixtures of correctly "and 2110 and Fe O at 1150 C. in air. Then a mixture of 15.72 gs. of BaFe O 20.88 gs. of BaFe O and l6.0 6 gs. of ZnFe O which corresponds to the desired compound BaZnFe O was ground for 4 hours with ethyl alcohol in a vibration mill, after which rings were molded .irom this product at a pressure of 1000 kg s./cm. these rings were fired for one hour at 1180 C. in oxygen. X-ray examination'proved that in this manner a fairly purecompound with the desired structure was obtained.

rings are indicated in the table The properties of the ErampleX BaCbg and in the molecular ra io 0i 1:5 .6

, v.lBaZ nFegs tm u chosen proportions of BaCO and FeO BaCO and F 0,, 5

about 5.9 A.

1 While We have described our invention in connection with specificembodiments and applications, other modifications thereof will be readily apparent to thoseskilled this art without departing fromthe spirit andscope .of the invention as defined in the appended claims.

What we claim is:

1. A ferromagnetic material consisting essentially of crystals of a composition having the formula:

in which M is at least one divalent metal selected from the group 1 consisting of Mn, Fe, Co, Ni, Cu, Zn, and Mg, and

a has a value less than 0.5 (b+c) has a value less than 0.25 (e-l-f) has a value less than 0.6

said crystals having a rhombohedric structure, of which the unitcell in thehexagonal. crystal systemcan belde ,scribed with a c-axis of about 43.5 A. and an .a-axis of -2. .Aierromagnetic body having an initial pemeability exceeding). at a frequency of at least 50mc./sec..consistof a composition perature of about 1000,to 1300"- C. for a time sufiicient consisting of Mn, Fe, Co, Ni, Cu, Zn, and -Mg, and

a has a value less than 0.5 (b+c) has a value less than 0.25 (e+f) has a value less than.0.6

said crystals having a rhombohedric structure, of which the 'unit cell in the hexagonal crystal can be described with a c-axis of about 43.5 A. and ana-axis of about 5.9 A. 1

3. A permanent magnet comprising a magnetized highly-coherent body consisting essentially of crystals of a composition having the formula:

in which M is at least one divalent metal selected from the group consisting of Mn, Fe, Co, Ni, Cu, Zn, and Mg, and

a has a value less than 0.5

(b-l-c) has a value less than 0.25 (e-l-f) has a value less than 0.6

said crystals having a rhombohedric structure of which the unit cell in the hexagonal crystal system can be described with a c-axis of about 43.5 A. and an a-axis of about 5.9 A.

4. A method of producing a ferromagnetic material which comprises the steps, forming a finely-divided mixture of oxides in proportions forming upon heating crystals of a composition having the formula:

to form said latter crystals.

. 6. A method o produci g a: ferromagnetic material comprising the steps, forming a, finely-divided mixture 1 of divalent metal oxides inproportions forming upon subsequent heating crystals of a composition,. having the formula: Y

a n 1.i s t btC sMF e e+r 1 u in which, i i f M is a divalent metalselectedfrom the group of Mn, Fe, Co, Ni, Cu, ZnQand Mg, and z'zhas a'valueless-than0.5 f t (b+c) has a value less than 0:25

(e+f) has a value less than 0.6,

said crystals having a rhombohedric structure, of -which the unit cell can bedescribed with a c-axis of about 43 .5 A. and an a-axis of about 5.9 A.; heating said mixture to a temperature between about 900 to 1200 C. to react the same; finely-dividing the reaction product; and heating the finely-divided reacted product in an atmosphere containing at least as much oxygen as air to a temperature of about 1000" to 1300 C. for a time suflicient to form said crystals.

7. A method of producing a ferromagnetic body which comprises the steps forming a finely-divided mixture of oxides in proportions forming upon heating crystals of a composition having the formula:

Ba 5 ,1 SI Pb C MnFeg +nA1 CIgQn in which i M is a divalent metal selected from the group consisting of Mn, Ife, Co, Ni, Cu, Zn, and Mg, and ahas a value less than 0.5 e 5 (b'+c) has a value less than 0.25 (e+ f) has a value less than 0.25,

said crystals having a rhombohedrio structure, of which the unit cell in the hexagonal system can be described consisting -Y'With a c-axis of about 43.5 A.,and an a-axis of about 5.9 A.'; compacting said mixture into a body of desired shape and dimensions; and heating said compacted body inan'a'tmosphere containing at least as much oxygen as with a c-axis of about 43.5 A. and an a-axis of about i 5.9 A.; and heating said mixture in an atmosphere containing at least as much oxygen as air at a temperature of about 1000" to 1300 C. for a time sutiicient tojform said crystals.

5. A method of producing a ferromagnetic material comprising the steps, forming a finely-divided mixture of divalent metal oxides and ferric oxide in proportions yielding upon heating crystals having a structure corre 'sponding to that of the mineral mangetoplumbite; heating said mixture at a temperature below 1100" C. and sufficiently high to form said crystals; mixing said crystals with additional oxides of divalent metals in amountssufficient to form upon heating crystals of a composition having the formula:

said latter crystals having a rhombohedric structure, of which the unit cell in the hexagonal system can be described with a c-axis of about 43.5 A. and an 'a-axis of about 5.9 A.; and heating the latter mixture in an atmosphere containing at least as much oxygen as air to a temair at a temperature of about 1000 to 1300 C. for a time sufiicient to form said crystals.

8. A method of producing a permanent magnet body which comprises the steps forming a finely-divided mixture of oxides in proportions forming upon heating crystals of a composition having the formula:

Ba Sr Pb Ca M Fe CHO;

in which M is a, divalent metal selected from the group consisting of Mn, Fe, Co, Ni, Cu, Zn, and Mg, and a has a value less than 0.5

(b-l-c) has a value less than 0.25 (e-H) has a value less than 0.25,

said crystals having a rhombohedric structure, of which the unit cell in the hexagonal system can be described with a c-axis of about 43.5 A. and an a-axis of about 5.9 A.; compacting said mixture into a body of desired shapes and dimensions; heating said compacted body in 2,659,698 Berge Nov. 17, 1953 (Other references on following page) 9 UNITED STATES PATENTS Harvey Nov. 8, 1955 Crowley Feb. 28, 1956 Went Sept. 11, 1956 Gorter et a1. Sept. 11, 1956 Crowley Jan. 22, 1957 Medvediefi Mar. 25, 1958 FOREIGN PATENTS 1 10 France Apr. 13, 1955 OTHER REFERENCES Erchalk et al.: J. Amer. Chem. Soc., October 1946, pp. 2085-2093.

Harvey et al.: RCA Reviewyseptember '1950, p. 346.

Phillips Technical Review, vol. 13, No. 7, pp. 194-208.

Phillips Technical Review, vol. 18, No. 6, pp. 145-154.

Patent should read as corrected below.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2346 753 Gerard Heinrich Jonker et a1.

July 26V 1960 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters c-axis line Column 2; line l3 for. "coaxis" read a I 14L, for an axis" read an a-axis line 57,, for "pentonlte" read bentonite column 7 line 16 and column 8 1l1ne 47 for "permanent magnet" eachoccur'ren'ce' read-'- ferromagnetic bod-y I Attes ting Ofiicer Signed and sealed this 10th day of January 1961.

(SEAL) Attest:

KARL H, AXLINE r ROBERT c. WATSUN Commissioner of Patents 

1. A FERROMAGNETIC MATERIAL CONSISTING ESSENTIALLY OF CRYSTALS OF A COMPOSITION HAVING THE FORMULA: 